A commonly used oil combustion boiler includes a furnace that is hollow inside and is placed in a vertical direction, and a plurality of combustion burners is provided along a circumferential direction on the wall of the furnace and is placed in a plurality of stages in a perpendicular direction. The combustion burner produces a flame by turning a liquid fuel into a spray with an atomizing medium and blowing the atomized liquid fuel into the furnace so as to enable the combustion in the furnace. A flue gas duct is connected to the upper portion of the furnace. The flue gas duct is provided, for example, with a superheater, reheater, economizer for recovering the heat of the flue gas. This causes the heat exchange between the flue gas generated by the combustion in the furnace and water. This can generate steam.
The combustion burner used in the oil combustion boiler is provided with a burner tip at the front end portion of the supply pipe of the liquid fuel and atomizing medium. The burner tip can jet the liquid fuel and atomizing medium from a plurality of jet holes formed on the front end after mixing the liquid fuel and the atomizing medium. When a fuel that generates a lot of NOx or soot dust, such as a heavy fuel, is used in the burner tip, the reduction in the NOx or soot dust is required while a high combustibility is maintained. In light of the foregoing, the increase in the number of jet holes in the burner tip can be considered. However, the increase in the number of jet holes shortens the distance between the adjacent jet holes. This causes the jet flows to interfere with each other and each of the jet flows to get into a film state. This makes it difficult to take in the surrounding air. There is a risk of ignition failure or combustion failure.
A burner tip configured to solve the problem is described, for example, in Patent Literature 1. An internal mixing type atomizer described in Patent Literature 1 is provided with a fuel supply passage, an atomizing medium supply passage that atomizes the fuel, a mixing chamber that mixes the fuel supplied from the fuel supply passage with the atomizing medium supplied from the atomizing medium passage, and an jet hole that jets a mixed fluid in the mixing chamber to the outside. Furthermore, in the burner tip described in Patent Literature 2, a plurality of atomizing medium jet holes radially extends from an atomizing medium chamber, and a mixture jet hole is formed as an extension of each of the front ends and the mixture jet holes open on the front end of the burner tip. A fuel jet hole extends from a liquid fuel chamber and the front end of the fuel jet hole opens on the side surface of the mixture jet hole.